Horsetails (Equisetaceae) are perennial, ornamental plants that grow from creeping rhizomes. They look like miniature bamboos because of their single hollow, jointed stem with bristle-like branches. During prehistoric times, they grew as large trees. The plant's weed-like properties contribute to their invasive nature; however, when planted properly, they can be a good addition to any type of garden. Different varieties are available in nurseries. Choose the type that will suit your garden best.
Also known as swamp horsetail, water horsetail (Equisetum fluviatile L.) is a slender, dark green plant that has hollow, jointed stems measuring up to 40 inches high, which are devoid of flowers and true leaves. The stems have 10 to 30 longitudinal ridges and thin walls, which makes them weak. Instead of flowers and fruits, a water horsetail has cone-like, spore-producing structures that appear at the ends of the fertile stems. The water horsetail's rough texture and corrugated stems are some of its main identifying features. Appearing at each joint are whorls of tiny, black-tipped scales or whorls of long branches joined together. The cones at the stem tip produce the spores. Often producing a dense population near shorelines and in shallow water, water horsetail is an ideal plant for a bog or water garden.
Field horsetail (Equisetum arvense L.) consists of two types of stems (sterile and fertile) that appear every year from rhizomes. The rhizomes are fleshy and tuberous, measuring up to 3/4 inch in diameter, and can grow in singles or in pairs at the joints. Fertile stems do not have chlorophyll and die down after shedding spores. They have dark, creeping, brown-woolly rhizomes and are tuberous in nature. The stems measuring up to 4 inches long are brittle, unbranched and have a spore-bearing end. They also appear similar to asparagus sprouts at first glance. Sterile stems measuring up to 2 feet are tough, wiry and appear after the fertile stems and die down in fall. Whorls of numerous green branches appear from the joints. The stems have 10 to 12 ridges. Sterile stems appear more often than fertile stems do.
Scouring Rush Horsetail
Leafless, dark evergreen stems that are all fertile and do not die back in autumn differentiates the scouring rush (Equisetum hyemale) from the field horsetails. The stems appear similar to those of the field horsetails; however, they are green with two black ring-like bands at the joints. Each stem can reach up to 4 feet tall upon maturity and has a spore-bearing cone, known as a strobilus, that appears on top in various shades of brown. Scour rush are predominant in the banks of ditches, or borders of waterways and reservoirs of the Pacific Northwest. Plant scouring rush in ponds and bog gardens using containers to prevent them from taking over the garden.